Degradation Kinetics and Antioxidant Activity of Anthocyanin from Hibiscus sabdariffa L.

The degradation kinetics of anthocyanins from Hibiscus sabdariffa L. under different pH value, temperature and stabilizer, as well as the antioxidant activity of those anthocyanins during heat treatment were studied. The results showed that the degradation of anthocyanins was in accordance with the first-order kinetic equation, the thermal stability of anthocyanins under pH<3 were stronger than pH ≥ 3.The degradation rate k of anthocyanins increased with the increase of temperature while the half-life t_1/2 of degradation decreased at same pH value. The anthocyanins showed the lowest (0.2539 h^-1) and the highest (0.6547 h^-1) degradation rate constant, and the maximum (2.73 h) and the minimum (1.06 h) half-life value at pH2.0, 80℃ and pH5.0, 100℃, respectively. The degradation rate constant for anthocyanins decreased with stabilizer content increase at 80, 90 and 100℃. Meanwhile, the antioxidant capacity in vitro of anthocyanins of Hibiscus sabdariffa L. decreased significantly after heat treatment at 80, 90 and 100℃ for 2.5 h (p<0.05). The addition of CMC and sodium alginate could significantly improve the oxidation stability of anthocyanins and the effect of sodium alginate was better than that of CMC.